Sealing substrate, method of fabricating the same, display device, and electronic instrument

ABSTRACT

A sealing substrate has first and second substrates. A hollow portion is formed in a first surface of the first substrate. The first substrate has a plate portion that forms a bottom surface of a hollow portion and a frame portion that forms an inner wall surface of the hollow portion. The second substrate is affixed to a second surface of the first substrate. The second substrate is formed of a material having a lower specific gravity than that of the first substrate.

This is a continuation of application Ser. No. 10/347,262 filed Jan. 21,2003, which is hereby incorporated by reference in its entirety.Japanese Patent Application No. 2002-12884, filed on Jan. 22, 2002, ishereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a sealing substrate, a method offabricating the sealing substrate, a display device, and an electronicinstrument.

A sealed structure is used for elements that use light-emittingmaterials and electrodes that are susceptible to the effects of moistureor oxygen, such as organic electroluminescent (EL) elements. A sealingsubstrate that is used in the art for sealing in an organic EL elementis formed by carving out a glass substrate. The thickness of the glasssubstrate is determined in accordance with the depth of the carving. Ifa deep carving is formed in a thin glass substrate, the strength of thesealing substrate will be insufficient. To ensure strength, the sealingsubstrate is made thicker and heavier. It is possible to form astructure that has both a thick bonding layer with the organic EL paneland also a deep carving, but in such a case large amounts of moistureand oxygen permeate through the bonding layer.

BRIEF SUMMARY OF THE INVENTION

A sealing member in accordance with one aspect of the present inventioncomprises:

a first substrate which has a hollow portion formed in a first surfacethereof, a plate portion forming a bottom surface of the hollow portionand a frame portion forming an inner wall surface of the hollow portion;and

a second substrate attached to a second surface of the first substrate,

-   -   wherein the second substrate is formed of a material of a        specific gravity lower than a specific gravity of the first        substrate.

A display device in accordance with one aspect of the present inventioncomprises:

the above-described sealing substrate; and

a display section that has been sealed in by the sealing substrate.

An electronic instrument in accordance with one aspect of the presentinvention comprises the above-described display device.

A method of fabricating a sealing substrate in accordance with oneaspect of the present invention comprises:

attaching a second plate-shaped member to a first plate-shaped member,then forming a hollow portion that is dug out of a surface of the firstplate-shaped member on the opposite side to the surface on which thesecond plate-shaped member is attached,

wherein the second plate-shaped member is formed of a material having aspecific gravity that is less than a specific gravity of the firstplate-shaped member.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 shows a sealing substrate and display device in accordance with afirst embodiment of the present invention.

FIG. 2 is illustrative of the method of fabricating a sealing substratein accordance with the first embodiment of the present invention.

FIG. 3 further is illustrative of the method of fabricating a sealingsubstrate in accordance with the first embodiment of the presentinvention.

FIG. 4 shows a sealing substrate and display device in accordance with asecond embodiment of the present invention.

FIG. 5 is illustrative of the method of fabricating a sealing substratein accordance with the second embodiment of the present invention.

FIG. 6 is illustrative of another method of fabricating a sealingsubstrate in accordance with the second embodiment of the presentinvention.

FIG. 7 shows a sealing substrate and display device in accordance with athird embodiment of the present invention.

FIG. 8 is illustrative of a substrate on which a display section isformed.

FIG. 9 is illustrative of the display section.

FIG. 10 shows an electronic instrument in accordance with an embodimentof the present invention.

FIG. 11 shows another electronic instrument in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The objective of embodiments of the present invention is to make alighter sealing substrate without insufficiency of strength or increasein the permeation of moisture or oxygen.

(1) A sealing substrate in accordance with one embodiment of the presentinvention comprises:

a first substrate which has a hollow portion formed in a first surfaceof the first substrate, a plate portion forming a bottom surface of thehollow portion and a frame portion forming an inner wall surface of thehollow portion; and

a second substrate attached to a second surface of the first substrate,

wherein the second substrate is formed of a material of a specificgravity lower than a specific gravity of the first substrate.

This embodiment of the present invention makes it possible to make thesealing substrate lighter, by forming the second substrate of a materialof a specific gravity less than that of the first substrate. Since thesecond substrate is attached to the first substrate, the strength of thefirst substrate in which the hollow portion is formed is notinsufficient. Since a deep hollow portion can be formed in the firstsubstrate, it is not necessary to provide a thick bonding layer forbonding the sealing substrate, which prevents any additional permeationof moisture or oxygen.

(2) With this sealing member,

first substrate may be formed of an inorganic oxide.

(3) With this sealing member,

the second substrate may be formed of resin.

(4) With this sealing member,

the second substrate may be a single layer.

(5) With this sealing member,

the second substrate may be formed of a material including a resinselected from a group of polyolefine, polyester, an ethylene vinylacetate copolymer, an ethylene methyl methacrylate copolymer, andionomer resin.

(6) With this sealing member,

the second substrate may comprise a plurality of layers.

(7) With this sealing member,

the second substrate may comprise a base material layer and a layer forbonding or adhesion.

(8) With this sealing member,

the base layer may be formed of a material including a resin selectedfrom a group of polyethylene terephthalate, a polyamide, polyolefine, apolycarbonate, a polyimide, polyethel sulfonic acid, an epoxy compound,polystyrene, and a cellulose resin; and

the layer for bonding or adhesion may be formed of a material includinga resin selected from a group of silicone, an acrylic resin, ametacrylic resin, an epoxy compound, polyurethane, an ethylene vinylacetate copolymer, and styrene-butadiene rubber.

(9) With this sealing member,

the second substrate may further comprise a buffer layer.

(10) With this sealing member,

the buffer layer may be formed of a material including a resin selectedfrom a group of styrene-butadiene rubber, silicon rubber, latex, andpolyurethane.

(11) With this sealing member,

the first substrate may be formed of an inorganic oxide selected from agroup of glass, quartz, and ceramic.

(12) With this sealing member,

the first substrate may be formed of a glass selected from a group ofsoda-lime glass, borosilicate glass, aluminosilicate glass, and silicateglass.

(13) With this sealing member,

the thickness of the first substrate may be within the range of greaterthan or equal to 0.1 mm but less than or equal to 1.1 mm;

the height of the inner wall surface of the hollow portion may be withinthe range of greater than or equal to 0.05 mm but less than or equal to0.8 mm; and

the thickness of the plate portion may be within the range of greaterthan or equal to 0.01 mm but less than or equal to 0.9 mm.

(14) With this sealing member,

the thickness of the second substrate may be within the range of greaterthan or equal to 0.01 mm but less than or equal to 0.4 mm.

(15) With this sealing member,

the total thickness of the first and second substrates may be within therange of greater than or equal to 0.1 mm but less than or equal to 1.5mm.

(16) A display device in accordance with one embodiment of the presentinvention comprises:

the above-described sealing substrate; and

a display section encapsulated with the sealing substrate.

(17) An electronic instrument in accordance with one embodiment of thepresent invention comprises the above-described display device.

(18) A method of fabricating a sealing member in accordance with oneembodiment of the present invention comprises:

attaching a first plate-shaped member to a second plate-shaped member,digging out of a surface of the first plate-shaped member to form ahollow portion on the opposite side to the surface on which the secondplate-shaped member is attached,

the second plate-shaped member being formed of a material having aspecific gravity that is less than a specific gravity of the firstplate-shaped member.

This embodiment of the present invention makes it possible to make thesealing substrate lighter, by forming the second plate-shaped member ofa material of a specific gravity that is less than that of the firstplate-shaped member. Since the second plate-shaped member is attached tothe first plate-shaped member, the strength of the first plate-shapedmember in which the hollow portion is formed is not insufficient. Sincea deep hollow portion can be formed in the first plate-shaped member, itis not necessary to provide a thick bonding layer for bonding thesealing substrate, which prevents any additional permeation of moistureor oxygen.

(19) In this method of fabricating a sealing member, the attaching stepmay comprise:

attaching a film sheet having a thermoplastic resin on a bondingsurface; and

pressing the second plate-shaped member against in the direction of thefirst plate-shaped member while being heated.

(20) In this method of fabricating a sealing member, the secondplate-shaped member may include a base material member and a member forbonding or adhesion; and

the attaching step may comprise attaching the base material member tothe first plate-shaped member for bonding or adhesion.

(21) In this method of fabricating a sealing member, the attaching stepmay comprise:

providing a molten resin for forming the second plate-shaped member maybe provided on the first plate-shaped member.

(22) In this method of fabricating a sealing member, the digging stepmay comprise:

forming a plurality of the hollow portions may be formed in the firstplate-shaped member; and

may further comprise cutting the first and second plate-shaped membersmay be cut at each of the hollow portions, to obtain a plurality ofsealing members.

These embodiments of the present invention are described below withreference to the accompanying figures.

First Embodiment

A sealing substrate and display device in accordance with a firstembodiment of the present invention is shown in FIG. 1. The displaydevice is an organic electroluminescent (EL) panel, by way of example.The display device has a substrate 100, a display section 102, and asealing substrate 104. At least the display section 102 is sealed in bythe sealing substrate 104. The space sealed in thereby could be filledwith nitrogen or it could be in a vacuum. The display device could alsohave a drying agent 106. This display device emits light that has beengenerated by the display section 102 towards the substrate 100 side. Inother words, an image is displayed on the substrate 100 side.

The sealing substrate 104 has a first substrate 10. The sealingsubstrate 104 is either impermeable to oxygen or moisture or is onlybarely permeable. The first substrate 10 could be formed of an inorganicoxide, such as glass (soda-lime glass, borosilicate glass,aluminosilicate glass, or silicate glass), quartz, or ceramic. The firstsubstrate 10 could have optical transmissivity, or it could beconfigured to pass only light of a specific wavelength, or it could beimpermeable to light. In other words, the first substrate 10 could beeither transparent or non-transparent, or it could function as a colorfilter. The thickness of the first substrate 10 could be within therange of greater than or equal to 0.1 mm but less than or equal to 1.1mm.

A hollow portion 12 is formed in a first surface of the first substrate10. The first substrate 10 has a plate portion 14 that forms a bottomsurface of the hollow portion 12 and a frame portion 16 that forms aninner wall surface of the hollow portion 12. The frame portion 16 is ofa shape that surrounds greater than or equal to the display section 102.The frame portion 16 could be of an angular ring shape. The inner wallsurface of the hollow portion 12 could be either perpendicular to thebottom surface, as shown in FIG. 1, or at an oblique angle thereto.

The depth of the hollow portion 12 (in other words, the height of theinner wall surface) is preferably greater than or equal to the totalthickness of the display section 102 and the drying agent 106 (ifprovided). By way of example, the height of the inner wall surface couldbe greater than or equal to 0.05 mm but less than or equal to 0.8 mm.The thickness of the plate portion 14 could be greater than or equal to0.01 mm but less than or equal to 0.9 mm.

The sealing substrate 104 has a second substrate 20. The secondsubstrate 20 is affixed to a second surface of the first substrate 10(the surface on the opposite side to the hollow portion 12). Theaffixing of the second substrate 20 ensures that the strength of thefirst substrate 10 in which the hollow portion 12 is formed is notinsufficient. The second substrate 20 is affixed to at least the plateportion 14. The second substrate 20 could be affixed in such a manner asto extend over the frame portion 16. The second substrate 20 is formedof a material having a specific gravity that is less than that of thefirst substrate 10. This makes it possible to design a lighter sealingsubstrate 104. If the first substrate 10 is formed of an inorganicoxide, by way of example, the second substrate 20 could be formed of aresin. The thickness of the second substrate 20 could be greater than orequal to 0.01 mm but less than or equal to 0.4 mm.

The second substrate 20 could be formed of a plurality of layers. Thesecond substrate 20 shown in FIG. 1 has a base layer 22 and a layer 24for bonding or adhesion. The base layer 22 could be formed of a resinthat is any one of polyethylene terephthalate, a polyamide, polyolefine,a polycarbonate, a polyimide, polyether sulfonic acid, an epoxycompound, polystyrene, or a cellulose resin. The layer 24 for bonding oradhesion could be formed of a resin that is any one of silicone, anacrylic resin, a metacrylic resin, an epoxy compound, polyurethane, anethylene vinyl acetate copolymer, or styrene-butadiene rubber. The layer24 for bonding or adhesion is preferably attached hermetically to thefirst substrate 10.

The sealing substrate 104 is affixed to the substrate 100 (the substratein which the display section 102 is formed) by a bonding layer. Withthis embodiment, the hollow portion 12 is formed to be deep, so it isnot necessary to make the bonding layer 26 thick. This therefore ensuresthat there is no further addition in the permeability of moisture oroxygen into the region sealed by the sealing substrate 104. It would besufficient to provide the bonding layer 26 with a thickness ofapproximately 1 to 10 μm, or about 3 μm or 5 μm, by way of example. Thethickness of the sealing substrate 104 (the total thickness of the firstand second substrate 10 and 20) could be greater than or equal to 0.1 mmbut less than or equal to 1.5 mm.

The sealing substrate 104 in accordance with this embodiment has theconfiguration described above, and the method of fabrication thereof isdescribed below. The method of fabricating the sealing substrate 104includes a first plate-shaped member 30 to which is attached a secondplate-shaped member 32, as shown in FIG. 2. If necessary, the first andsecond plate-shaped members 30 and 32 are cut to form theabove-described first and second substrates 10 and 20. The secondplate-shaped member 32 has a member for foundation 34 (which forms theabove-described base layer 22) and a member for bonding or adhesion 36(which forms the above-described the layer 24 for bonding or adhesion).A peel-off sheet 38 is pasted to the member for bonding or adhesion 36,and the first plate-shaped member 32 is attached to the secondplate-shaped member 30 while this sheet is being peeled off. The memberfor bonding or adhesion 36 is used for handling.

At least one hollow portion 12 (a plurality thereof in FIG. 3) issubsequently formed in the first plate-shaped member 30, as shown inFIG. 3. More specifically, each hollow portion 12 is formed in a surfacethat is on the opposite side of the first plate-shaped member 30 fromthat to which the second plate-shaped member 32 is affixed. Theformation of the hollow portions 12 could be done by any one ofsand-blasting, etching (such as wet etching), carving, or grinding. Withthis embodiment, the attachment of the second plate-shaped member 32makes it possible to prevent damage to the first plate-shaped member 30.

The first and second plate-shaped members 30 and 32 are cut as necessaryfor each hollow portion 12 if a plurality of hollow portions 12 has beenformed, or for one hollow portion 12. Since the first plate-shapedmember 30 is attached to the second plate-shaped member 32, no damage iscaused during cutting and transportation (such as during transportationby suction). Note that if the second plate-shaped member 32 is providedaway from the cutting lines, only the first plate-shaped member 30 iscut. This makes it possible to obtain the sealing substrate 104 (seeFIG. 1). In the example shown in FIG. 3, a plurality of the sealingsubstrates 104 (the first and second substrates 10 and 20) can beobtained.

Since the first substrate 10 has the second substrate 20 attachedthereto, it is possible to prevent damage while attaching it to thesubstrate 100 or while attaching the drying agent 106. Note that if thestep of attaching the sealing substrate 104 is done in a dryenvironment, there will be no incursion of moisture into the sealedspace. Making the sealing substrate 104 thinner and lighter ensures thatthe display device can also be thinner and lighter. In the displaydevice, the second substrate 20 that forms a surface layer of thesealing substrate 104 is formed of a resin, so it improves the shockresistance. The sealing substrate 104 can be shielded from oxygen andmoisture by the first substrate 10.

Second Embodiment

A sealing substrate and display device in accordance with a secondembodiment of the present invention is shown in FIG. 4. The sealingsubstrate of the display device of FIG. 4 has a single-layer secondsubstrate 40. In all other points, the configuration is as described forthe first embodiment. The single-layer second substrate 40 could beformed of a resin that is any one of polyolefine, polyester, apolyethylene vinyl acetate copolymer, or a polyethylene methylmethacrylate copolymer.

The method of fabricating this sealing substrate is illustrated in FIG.5. In the example of FIG. 5, a second plate-shaped member 42 is asingle-layer or multi-layer sheet having a thermoplastic resin on abonding surface side. The second plate-shaped member 42 is pressed inthe direction of the first plate-shaped member 30 while heat is appliedthereto. A roller 44 could be used to apply the pressure, and the heatcould also be applied by the roller 44. The second plate-shaped member42 can be attached to the first plate-shaped member 30 in this manner.Subsequent steps are as described with reference to the firstembodiment.

Another method of fabricating the sealing substrate is illustrated inFIG. 6. In the example of FIG. 6, the second plate-shaped member isformed on the first plate-shaped member 30 by providing molten resin 46on the first plate-shaped member 30. The molten resin 46 could besupplied from a dispenser 48. Subsequent steps are as described withreference to the first embodiment. The sealing substrate in accordancewith this embodiment exhibits the operational effects that weredescribed with reference to the first embodiment.

Third Embodiment

A sealing substrate and display device in accordance with a thirdembodiment of the present invention is shown in FIG. 7. The sealingsubstrate of the display device of FIG. 7 has a second substrate 50 thatis formed from a plurality of layers. The second substrate 50 has abaselayer 52, a layer 54 for bonding or adhesion, and a buffer layer 56.Note that the layer 54 for bonding or adhesion could be omitted. In allother points, the configuration is as described for the firstembodiment.

The buffer layer 56 forms a surface layer on the opposite side of thesealing substrate from the hollow portion 12. The buffer layer 56 isformed from a resin that is one of styrene-butadiene rubber, siliconrubber, latex, or polyurethane. The buffer layer 56 enables a furtherimprovement in shock resistance. The sealing substrate in accordancewith this embodiment exhibits the operational effects that weredescribed with reference to the first embodiment.

Other Embodiments

Details of the substrate 100 provided on the display section 102 of FIG.1 are shown in FIG. 8. The substrate 100 has optical transmissivity andcould be a glass substrate or plastic substrate. The display section 102is provided on the substrate 100 within the region that is sealed by thesealing substrate 104. A scan-side drive circuit 110 (together withwiring connected thereto) is formed on the substrate 100, for drivingthe display section 102. With this embodiment, the scan-side drivecircuit 110 (together with the wiring connected thereto) is also formedwithin the region that is sealed by the sealing substrate 104. Powerlines 112, 114, and 116 corresponding to the three colors red, green,and blue are formed on the substrate 100. Cathode wiring 118 is formedon the substrate 100. A flexible substrate 122 on which is mounted anintegrated circuit chip 120 is attached to the substrate 100. Theintegrated circuit chip 120 is connected electrically to the wiringformed on the substrate 100. The integrated circuit chip 120 has adata-side drive circuit.

Details of the integrated circuit chip 120 are shown in FIG. 9. Aplurality of switching elements 124 (such as thin-film transistors) areformed on the substrate 100 in the display section 102. The displaysection 102 has a plurality of light-emitting elements 130 that emitlight in a plurality of colors (such as the three colors red, green, andblue). The switching elements 124 control the light-emitting elements130. Each light-emitting element 130 includes a pixel electrode 132 anda cathode 136 (or rather, a part thereof), with a light-emitting layer134 therebetween. Each pixel electrode 132 is connected electrically tothe power lines 112,114, and 116 of FIG. 8. Each cathode 136 isconnected electrically to the cathode wiring 118 of FIG. 8. Thelight-emitting layer 134 emits light in accordance with a currentsupplied from the pixel electrode 132.

Neighboring light-emitting layers 134 are separated by bank portions138. The light-emitting layer 134 could be formed of a high-molecularsubstance or a low-molecular substance. If a high-molecular material isused as the light-emitting layer 134, it is important to shield it fromoxygen and moisture, so use of the sealing substrate of the presentinvention is effective therefor.

A notebook type of personal computer 1000 shown in FIG. 10 and a mobilephone 2000 shown in FIG. 11 are examples of electronic instrumentshaving the display device in accordance with embodiments of the presentinvention.

The present invention is not limited to the above-described embodiments,and various modifications can be made. For example, the presentinvention includes various other configurations substantially the sameas the configurations described in the embodiments (in function, methodand effect, or in objective and effect, for example). The presentinvention also includes a configuration in which an unsubstantialportion in the described embodiments is replaced. The present inventionalso includes a configuration having the same effects as theconfigurations described in the embodiments, or a configuration able toachieve the same objective. Further, the present invention includes aconfiguration in which a publicly known technique is added to theconfigurations in the embodiments.

1. A sealing substrate comprising: a first substrate which has a hollowportion formed in a first surface of the first substrate, a plateportion forming a bottom surface of the hollow portion and a frameportion forming an inner wall surface of the hollow portion; and asecond substrate attached to a second surface of the first substrate,wherein the second substrate is formed of a material of a specificgravity lower than a specific gravity of the first substrate.